Field of the Invention
The present invention relates to a touch display device for sensing a touch position and a force and a method of driving the same.
Discussion of the Related Art
Instead of input devices such as a mouse or a keyboard which is conventionally applied as an input device for liquid crystal display (LCD) devices, a touch panel that enables a user to directly input information through a screen with a finger or a pen is being applied to display devices. Since all users can easily manipulate the touch panel, the application of the touch panel is being expanded.
Recently, LCD devices to which a touch panel is applied are being developed in a type where a touch sensor is built into a liquid crystal panel, for slimming the LCD devices. In the following description, the touch panel denotes that the touch sensor is built into a display panel (or a liquid crystal panel or an organic light emitting diode (OLED) panel).
Touch panels are categorized into a resistive type, a capacitance type, an infrared type, etc. depending on a touch sensing method. Recently, since the capacitance type touch panel provides convenience in a manufacturing process and is good in touch sensitivity, the capacitance type touch panel is attracting much attention. Capacitance type touch panels are categorized into a mutual capacitance type and a self-capacitance type.
FIG. 1 is a diagram schematically illustrating a cross-sectional structure of a related art touch panel 1.
Referring to FIG. 1, the related art touch panel 1 includes a lower substrate on which a plurality of pixels and a thin film transistors (TFT) array are provided, an upper substrate on which a color filter array is provided, a polarizing film, and glass. A pixel electrode and a common electrode are provided on the lower substrate (a TFT array substrate). In this instance, the common electrode is used for display, and moreover, is used as a touch electrode.
FIG. 2 is a diagram schematically illustrating touch electrodes of the related art touch panel 1. In FIG. 2, the touch panel 1 having an all point self-capacitance touch type where all touch electrodes are sensed in a self-capacitance type is illustrated.
Referring to FIG. 2, a plurality of touch electrodes 10 are formed by grouping the common electrode in units of a plurality of pixels. In order to sense a touch applied to all of the plurality of touch electrodes 10, the touch electrodes 10 are respectively connected to a touch driver 30 through a plurality of conductive lines 20.
The touch panel 1 having the all point self-capacitance touch type divides one frame period into a display period and a touch period and performs a display driving operation and a touch sensing operation in a time division type.
In the display period, a pixel voltage is supplied to the pixel electrode, and a common voltage is supplied to the common electrode (the touch electrode), thereby displaying an image. Also, in the touch period, a touch driving signal is supplied to the touch electrodes 10 corresponding to the common electrode, and then, a capacitance of each of the touch electrodes 10 is sensed, thereby determining whether there is a touch and detecting a touch position. In the related art touch panel 1, since only a touch position based on the presence of a touch is detected, a user interface provided to a user is simple.
Recently, interest in touch panels for sensing a force, applied thereto when a touch is being performed, in addition to determining whether there is a touch and detecting a touch position is increasing. Therefore, a touch panel for sensing a touch position and a force is disclosed in Korean Patent Registration No. 10-1033154. However, since the touch panel should individually include a first sensing unit for detecting a touch position and a second sensing unit for sensing a touch force, the touch panel is thick in thickness and is high in manufacturing cost.